Charging from the Car

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MTBJay

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Morning all looking in to buying a power invertor for the car so i can charge my Focus Jam2 with a 378 watt battery, im looking at buying a Bestek 300W power inverter DC12v to 230V
Would this work?

 
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No idea but basic maths tells me that 300 won't charge 378
 
And it certainly won't work from the cig lighter plug for very long.
 
Watts and Watt-Hours are not the same thing. How much power does the charger draw? I agree that it will be a big drain on the auto battery/alternator.
 
Your battery is 378 Watt Hours of storage. A measure of total energy stored. Whereas a 300W inverter is able to provide 300W of power continuously.

What size is your car ciggy lighter fuse and what power size is your battery charger?
 
As an example my charger (Levo SL) is specified as 100-240 V at 2.5 A max. I would expect the max is at 100 V so at 240 V maybe it takes about 1 A. That's still about 240 W and if the inverter is like most and slightly inflates the numbers it is getting close to the limit.

300 W at 12 V is 25 A, probably more than the cig lighter socket is made for. Even at 14 V it's over 20 A
If your charger specifies pure sine wave input then you need an inverter that does that (usually more $$$). I am looking at doing the same thing and thinking a dedicated 30 A power socket for the car and a 350 watt inverter may be the way to go.
 
MTBJay said:
Morning all looking in to buying a power invertor for the car so i can charge my Focus Jam2 with a 378 watt battery, im looking at buying a Bestek 300W power inverter DC12v to 230V
Would this work?

Click to expand...
The output of your charger is what matters, rather than the input voltage. I'm assuming it's 36V so output will be 42V-ish max at whatever amperage your charger specifies, be it 2-4amp. Watts is VxA so 42V x 4A =168W. Add 40W for losses (rough guesstimates here), and you're still well inside the inverters rated capacity.
As for the vehicles cigarette lighter output current, Most will max output 10-15amp at 12V which means a max output of 12 x 15 = 180W or 120W if the vehicle is 10A. This means your fag lighter socket will be running hot at full charge rate. Better to connect the charger directly to the vehicle battery, or fit a Merit plug to the inverter and a socket wired to the vehicle battery as these handle 20A at 12V.
As @boBE mentions, if your charger requires a pure sine inverter, then you need one of those. Most modern vehicles have high power alternators so charging whilst driving will be fine, otherwise it would be like leaving all the lights on and the stereo blasting :D

ps: I won't remove this post, but as @flash pointed out it contains inaccuracies, so please ignore what I said about the 300W inverter being up to the task. It won't be.
Rik.
 
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Has nothing to do with your battery and everything to do with your charger.....

Watts = volts x amps is the basic formula. Your charger will have listed how many amps it requires. Multiply that by 230 and you will see how many watts the inverter needs to be able to produce.

A 4 amp charger will need just under 1000 watts (taking into account inefficiencies in the system) and a 6 amp (like mine) will need 1500 watts. So it's highly unlikely a 300 watt inverter will do the job.

I have a 2000 watt inverter and 400 Amp of Lithium in my camper so I can charge batteries while camping.

Gordon
 
Flatslide said:
The output of your charger is what matters, rather than the input voltage. I'm assuming it's 36V so output will be 42V-ish max at whatever amperage your charger specifies, be it 2-4amp. Watts is VxA so 42V x 4A =168W. Add 40W for losses (rough guesstimates here), and you're still well inside the inverters rated capacity.
As for the vehicles cigarette lighter output current, Most will max output 10-15amp at 12V which means a max output of 12 x 15 = 180W or 120W if the vehicle is 10A. This means your fag lighter socket will be running hot at full charge rate. Better to connect the charger directly to the vehicle battery, or fit a Merit plug to the inverter and a socket wired to the vehicle battery as these handle 20A at 12V.
As @boBE mentions, if your charger requires a pure sine inverter, then you need one of those. Most modern vehicles have high power alternators so charging whilst driving will be fine, otherwise it would be like leaving all the lights on and the stereo blasting :D
Click to expand...

I think your vehicle inverter will need to be able to supply the INPUT current the battery charger requires, not the OUTPUT current it gives to the battery. You need to look at the AC requirements of the battery charger and go from there. What you've described above would be using a DC to DC system which would bypass the inverter and original factory charger.

As the inverter outputs AC power you need to work with that side of the bike charger.

Gordon

p.s. I have installed two of these charger systems in the last year (one in my Landrover and a bigger one in my caravan) and I'm currently installing a third in a van conversion.
 
flash said:
I think your vehicle inverter will need to be able to supply the INPUT current the battery charger requires, not the OUTPUT current it gives to the battery. You need to look at the AC requirements of the battery charger and go from there. What you've described above would be using a DC to DC system which would bypass the inverter and original factory charger.

As the inverter outputs AC power you need to work with that side of the bike charger.

Gordon

p.s. I have installed two of these charger systems in the last year (one in my Landrover and a bigger one in my caravan) and I'm currently installing a third in a van conversion.
Click to expand...
True. I forgot that a 300W 230V inverter is only 1.3A output. Ignore my bs, it's early morning here :LOL:
 
A little further investigation indicates that switching power supplies (most of ours are) do not work well (or at all) with "modified sine wave" inverters. Looking at oscilloscope traces of some inexpensive "pure" sine wave inverters they are more accurately "poor" sine waves. Most UPS are modified sine wave but we use them rarely and not for long.
Unless the manufacturer gives the ok to use modified sine wave I would probably not.
Ymmv ...
 
I’ve got a small solar setup in my workshop, for lighting and low 240v power requirements via a 450 Ah battery bank connected to a 1000w pure sine wave inverter.

I’ve got both the 4.0 and 4.5A versions of the Focus charger, and when connected to the inverter they power up fine and start the initial charging ok, but as the power ramps up to do the bulk charge they overwhelm the inverter.

I’m sure a beefier inverter would work fine, but I wouldn’t connect such a device to my car battery for long, not if I wanted to get home anyway!

If I was wanting to do it, I’d get a 2000w inverter and a suitable lifePo4 battery to put in the car somewhere.

Mind you, looking at the trail centre car parks these days, you need a VW T5 camper van?!
 
I have a Transit custom Limited van with a plug under handbrake to plug in power tool batteries, phone & laptop chargers etc would this be ok for an inverter? I have a Shimano slow charger for my esommet
 
Shjay said:
I have a Transit custom Limited van with a plug under handbrake to plug in power tool batteries, phone & laptop chargers etc would this be ok for an inverter? I have a Shimano slow charger for my esommet
Click to expand...
Probably fine
 
Shjay said:
I have a Transit custom Limited van with a plug under handbrake to plug in power tool batteries, phone & laptop chargers etc would this be ok for an inverter? I have a Shimano slow charger for my esommet
Click to expand...

These are only 300W output. So the answer is maybe. You'll probably be Ok for regular current but I'm not sure what peak power is. I have one in my Transit as well but haven't tested it.

Just try it. It won't hurt any of your equipment. If the bike wants more current it'll just trip the inverter. Likely it'll just charge slowly.

Gordon
 
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